This study seeks to understand the functions of bone-related proteins in the processes of mineralization, cellular regulation, physical organization and overall structure of bone. Our approach to this problem will be to conduct physical/chemical studies of the interactions of procollagen, procollagen fragments, bone Gla-protein, osteonectin, and alpha2HS- Glycoprotein with respect to their interactions with phospholipid membrane, mineral, collagen, and other protein constituents found in bone. We will explore the nature of an osteoblast-related antigen which appears to be developmentally regulated by vitamin D by describing its primary structure and developmental regulation in both bone derived and marrow derived cells. We will continue to pursue structural studies aimed at understanding the relationship between osteonectin-like proteins in bone and in platelets and the fragmentation of bone osteonectin and bone Gla-protein. We will exploit immunoassays already developed for type I and type III collagen, COOH propeptides to identify the nature of the natural collagen propeptide antigens found in blood and explore the utility of the expression of these antigens in studies of bone cell and bone regulation in vivo. Finally, we will attempt to exploit quantitative tools developed in our basic studies to evaluate bone formation and resorption in both normal and pathophysiologic states.